Pull and rotation mechanism for crystal growing apparatus



June 18, 1963 N. E. HAMILTON 3,094,006

PULL AND ROTATION MECHANISM FOR CRYSTAL GROWING APPARATUS Filed June 15,1960 2 Sheets-Sheet 1 INVENTOR.

NOBLE E. HAMILTON .2 y gda ATTORNEY June 18, 1963 N. E. HAMILTON3,094,006

PULL AND ROTATION MECHANISM FOR CRYSTAL GROWING APPARATUS Filed June 15,1960 2 Sheets-Sheet 2 32 f I I2 7 FIG.3'

FIG.4

INVENTOR. NOBLE E.HAM|LTON ATT NEY 3' Alfllun m W My Hm f H UnitedStates Patent 3,41%,006 PULL AND ROTATION MECHANISM FOR CRYSTAL GRGWINGAPPARATUS Noble E. Hamilton, Belmont, Mass, assiguor to CleviteCorporation, Cleveland, Ohio, a corporation of Ohio Filed June 15, 1960,Ser. No. 36,233 Claims. (Cl. 74-22) This invention relates to animproved pull and rotation mechanism adapted to be employed in a crystalgrowing apparatus, or the like. I

A number of crystal growing methods are well-known in the prior art. Forillustrating the applicability of the present invention let it beassumed that the crystal growing method necessitates the provision of anapparatus including a seed holder to which a crystal seed is secured.The seed holder is longitudinally movable to slowly immerse the crystalseed into a molten mass of semiconductive material allowing the melt toadhere to the seed. The withdrawal of the seed from the melt occurs at avery slow speed to permit the molten material to crystallize on theseed. The seed is rotated during the growing process to improvecharacteristics in the growing crystal, for instance the symmetricalcross-section.

The pulling and rotating action is of utmost critical nature as can bereadily deduced from the fact that pulling rates of .001 up to .006 inchper second are conventionally in use. Heretofore, such requirements havenecessitated pull and rotation mechanisms unusually complex andcumbersome in structure. I

One of the principal objects of this invention is to provide a mechanismof utmost simplicity for pulling a crystal seed out of the melt and forsimultaneously rotating the seed holder during the pulling and/orimmersing cycle. The device in accordance with the invention is ofsimple nature, enabling the elimination of numerous mechanical partspreviously required. The simplification has not only affected theinitial cost, the maintenance of the device, but also in additionthereto has enabled the construction of a crystal growing apparatusofsubstantially reduced heights as compared to conventional systems.

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawings, and itsscope will be pointed out in the appended claims.

Briefly, an aspect ofv the invention is in the provision of a pull androtation mechanism for a crystal growing apparatus which. comprisesdriving means, a shaft rotatably driven by -the driving means, annularfrictional coupling member formed of elastic material and surroundingportions of the shaft, a pull rod, a mounting member for securing thepull rod for rotation and longitudinal displacement and maintaining thepull rod in frictional engagement with the frictional coupling member, aroller rotatably mounted and in driving engagement with the pull rod,means securing the roller for angular variation of the longitudinal axisof the roller in respect to the axis of the pull rod so that uponchanging the angular relation of the axes a force component is exertedon the pull rod to longitudinally displace the latter.

FIGURE 1 is a vertical partlysectional view of the present invention andincludes pertinent portions of a crystal growing apparatus;

FIGURE 2 is an enlarged cross-sectional View taken on the line 2-2 ofFIGURE 1, illustrating the shaft assembly;

FIGURE 3 is a top plane view of the pull and rotation mechanism; and

FIGURE 4 is a side elevational View, partly in section,

ice

2 illustrating the gimbal mounted roller arrangement and the handle forangular adjustment of the gimbal.

This invention is primarily concerned with solutions to problemsconcerning a pull and rotation mechanism, and hence, the followingdescription is generally restricted to such subject matter; reference tothe crystal growing apparatus is only included where necessary toclarify the present invention.

Referring now to the drawings, numeral 1 denotes a crystal growingapparatus having a base portion 3 providing a crucible assembly, atubular structure member 5 is connected on one end to the base 3 and atthe other end to a support plate 7 upon which a pull and rotationmechanism assembly 9 is mounted. The latter assembly 9 includes a pullrod 30 the lower end of which protr-udes into the tubular structuremember 5 and is axially movable therein to transport a crystal seed 8carried in seed holder 10, connected to the pull rod 39, to and from thecrucible assembly 3.

More particularly, the pull and rotation mechanism 9 comprises a singleconstant speed non-reversible motor and speed reducing unit 12, seeFIGURE 3, suitably mounted to the support plate 7. The motor speedreducing unit 12 is mechanically coupled to a worm 14 by means of aconventional coupler and support brushing 16 to rotate a shaft member17. The shaft member 17 is rotatably mounted with its axis perpendicularto the horizontal support plate 7. The shaft includes annular frictionalcoupling means 36 which surrounds a portion of the shaft 17 and whichfrictionally engages the pull rod member St} to rotate the same, ashereinafter explained. The shaft 217, refer to FIGURE 2, is formed by acylindrical base 19, suitably welded to the support plate 7, and anothercylindrical member 20 is rotatably mounted on the cylindrical base 19.The base 19' and member 20 are axially aligned and a central bore 21extends through member 20 and into portions of base 19 to receive apartially threaded bolt 22 therethrough. "The bolt 22 rotatably connectsmember 20 to the base 19 by extending into threaded portion 24 with thebolt head 25 loosely abutting against a washer 27 which is interposedbetween a shoulder 28 and the head 25 of the bolt 22. To effect suitableaxial alignment of member 20 and base 19, member 20 has an end 29 ofreduced diameter which extends in a closely registering axial bore 26 ofbase 19. This arrangement permits relative axial movement of member 20with respect to the base without permitting longitudinal movement.

A gear 32 is secured to shaft member 20 by soldering it thereto. Thegear 32 is in meshing engagement with the corresponding worm 14translating rotary motion from the motor to drive shaft member 20 of theshaft 17. A radial shoulder 34, integrally provided on shaft member 20,forms a radial enlarged portion into which three radial grooves 40 aremachined to receive in each groove a friction drive O-ring 36. Theinside diameter of the Cl-rings 36 is substantialy equal to the minimumbase diameter of the groove 40 to provide a tight fitting O-ringarrangement, while the thickness of the O-rings is such to extend thelatter radially beyond the outermost radial surface of the worm gear 32to enable the O-rings to frictionally engage the pull rod 36". TheO-rings 36 are resilient and yield in the direction of travel and theyalso can roll slightly in their grooves. This permits flexible drivingconditions to adjust for the relative longitudinal movement of the driveshaft as it pulls the seed crystal while simultaneously rotating it.This arrangement gen erally pre-supposes that the pull rod is positionedso that its longitudinal axis is, nominally parallel with respect to thelongitudinal axis of the shaft 17.

The longitudinal movement of the pull rod 30 is effected by a roller 44rotatably secured in adjustable bearings 46 which are mounted within agimbal ring 48, the latter being angularly displaceable with respect tothe longitudinal axis of the pull rod 30.

A frame 50 is movably attached to the support plate 7 by screws 51extending through slots 52 in plate 7, as illustrated in FIGURE 3. Theframe has a square-like configuration and provides a central opening 53to receive gimbal ring 48 therein. The wall 54 defining the aperture 53is angularly inclined, see FIGURE 1, and the outside diameter of thering-like gimbal 48 varies inversely with respect to angular dimensionsof wall 54. The tolerance between gimbal ring 48 and frame 50 is suchthat the gimbal ring may suitably be angularly displaced within theframe to vary the angularity of the roller 44 with respect to the pullshaft.

The roller 42 is made of elastic material, a cloth filled micartamaterial has been found suitable, and forms a cone-like configuration atopposite ends 43 with the center portion 42 of the roller beingsubstantially cylindrical. The conical ends 43 of the roller 44 radiallyprotrude into an aperture 56 of the gimbal ring provided at oppositeends near the axial center thereof. Each aperture 56 is threaded toreceive the cylindrical bearing-like disk 46 made of bearing bronze andprovided with a conical indentation 47 to rotatably receive the conicalend portion 43 of the roller 44. The cylindrical center 42 of the rollerfrictionally engages, as aforementioned, the pull rod member 30.

In FIGURE 4 there is shown a flat plate lever arm 58 made of steel orother suitable rigid material. One end 59 of the plate has cut outtherefrom a semicircular portion with a radius substantially equal tothe inside radius of the gimbal ring. Lever arm end 59 is attached tothe gimbal ring 48 by means of rivets or machine screws 60. Set screws63 extend through lever arm 58 near the upper and outermost corner ofend 59 and abut against the frame member 50. The arm 58 extendsdownwardly from the gimbal ring and provides at its lower end a handle61 to angularly manipulate the gimbal ring. In order to adjust thepressure between the roller 44 and the pull rod 30 the set screws 63 areadjusted to force the gimbal ring to its extreme outer position, asshown in FIGURE 1, and the screws 51 are loosened and the frame 50 ismoved on the support plate to its outermost position. The combinedadjustment affords a simple and effective pressure control means.

The frame 50 carries a spring 64 (see FIGURE 3) and a detent ball 66within aperture 62. The location of aperture 62 is determined to providea common longitudinal axis with opening 53 of frame 50. The detent ball66 is engaged and urged by the spring 64 against the lever arm 58 tomaintain the arm in a predetermined angular position. This isaccomplished by providing a plurality of openings 68 (see FIGURE 4) incircular array on the lever arm 58 and axially aligning the centerthereof with the axial center of the aperture 62 of the frame 50. Theradius of each opening 68 is slightly less than the radius of the detentball 66. Consequently, when handle 58 is moved until a preselectedopening 68 registers with detent ball 66, the spring 64 causes portionsof the ball to protrude into and partially through the opening 68 of thelever arm. The larger diameter of the ball precludes the completeprojection of the ball through the opening 68, whereby a predeterminedlocking position of the frame with respect to the gimbal ring isachieved.

With the parts constructed and arranged as above described the mode ofeffecting longitudinal movement of the pull shaft is as follows: Whenthe longitudinal axis of the roller 44 is substantially parallel to thelongitudinal axis of the pull rod 30, the aforementioned roller is inneutral position and only rotary movement of the pull shaft is possible.By turning the location of the longitudinal axis of the roller 44 withrespect to the longitudinal axis of the pull shaft, while the rollerfrictionally engages the pull shaft, a force component is exerted on thepull shaft producing a longitudinal displacement of the pull rod 30. Inother words, by swinging the lever arm 58 secured to the gimbal ring 48the skew angle between the roller and the pull shaft may be varied,thereby varying the lead or pull per revolution on the pull shaft. Sincethe mechanical lock of the lever arm to the frame by means of detentball 66 and springs 64 in an aperture 62 is a fairly loose one, afurther refinement of the angular position may be effected by adjustingthe lower portion of the lever arm by means of a micrometer spindle stopassembly 70 (FIGURE 4).

Since the changing weight of the growing crystal during the pullingprocess changes the pull rate, the position of the frame 50 isadjustable with respect to the top plate as aforestated to vary theforce of the roller 44 bearing against the pull shaft. This influencesthe slippage between the elastic roller and the pull shaft. Since theslippage is also a function of longitudinal thrust on the pull shaft,the resultant pull rate is a function of the crystal weight and thisfunction is variable by the force between the roller and the pull shaft.Similarly, by suitably matching the force with which the rollerfrictionally engages the pull shaft the device can provide compensationfor the otherwise normal change in crystal composition which occurs withthe depletion of the liquid semiconductive melt volume. Herein, thesystem responds directly to liquid volume via crystal weight as opposedto time in conventionally programmed systems, where the normal variationin crystal size causes appreciable drift of the desired program from thepreset actual program.

To effect a smooth and suitable longitudinal movement of the pull rod 30a combined bearing sleeve 72 of noncontaminating material, for instancegraphite, is co-axially disposed with respect to the seed holder 10 andpull rod 30. The bearing sleeve 72 is substantially cylindrical and ashoulder 74 thereof is adapted to receive a weight compensating spring76. Tubular portion 78 of bearing sleeve 72 provides a bearing surface80 to guide the seed holder 10 and simultaneously establishes aprotective sleeve around the critical area.

While there have been described what at present are considered to be thepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is aimed,therefore, in the appended claims to cover all such changes andmodifications asfall within the true spirit and scope of the invention.

I claim as my invention:

1. A pull and rotation mechanism for crystal growing apparatuscomprising, in combination; driving means; shaft means rotatably drivenby said driving means; annular frictional coupling means formed ofelastic material surrounding portions of said shaft means; pull rodmeans mounted for rotation and longitudinal displacement; mounting meansmaintaining said pull rod means in frictional engagement with saidfrictional coupling means; roller means rotatably mounted and in drivingengagement with said pull rod means; gimbal means rotatably constructedand arranged to carry said roller means for angular variation of thelongitudinal axis of the roller in respect to said axis of the pull rodmeans so that upon changing the angular relation of the axes a forcecomponent is exerted on the pull rod means to longitudinally displaceand rotate said pull rod means.

2. A pull and rotation mechanism for crystal growing apparatuscomprising, in combination; driving means; shaft means rotatably drivenby said driving means; at least one radial groove on said shaft means;elastic O-ring means carried rollably within said groove; pull rodmeans; mounting means securing said pull rod means for rotation andlongitudinal displacement and holding portions of said pull rod means infrictional engagement with said O-ring; elastic roller means rotatablymounted and adapted to drivingly bear against said pull rod means; saidpull rod means being frictionally suspended between said elastic 'O-ringand said elastic roller means; means for mounting said roller means forangular variation of the longitudinal axis of said roller in respect tothe axis of said pull rod means so that upon changing the angularrelation of the axes a force component is exerted on said pull rod meansto longitudinally displace said pull rod means.

3. A pull and rotation mechanism for crystal growing apparatuscomprising, in combination; driving means; shaft means rotatably drivenby said driving means and having a radially arranged groove; elasticannular means rollably surrounding said groove; a pull rod means hav--ing a longitudinal axis substantially parallel with the longitudinalaxis of the shaft means; mounting means se curing said pull rod meansfor rotation and for longitudinal displacement and maintaining said pullrod means in frictional driving engagement with said annular means;roller means rotatably mounted and in driving engagement with said pullrod means; gimbal means constructed and arranged to rotatably carry saidroller means for angular variation of said longitudinal axis of theroller in respect to said axis of the pull rod means so that uponchanging the angular relation of the axes a force component is exertedon said pull rod means to longitudinally displace and rotate said pullrod means.

4. A pull and rotation mechanism for crystal growing apparatuscomprising, in combination; driving means; shaft means engaging saiddriving means; gear means mounted on said shaft means and in operativecontact with said driving means to rotate said shaft means; O-ring meanssurrounding portions of said shaft means; pull rod means having alongitudinal axis substantially parallel with the longitudinal axis ofthe shaft means; mounting means securing said pull rod means forrotation and for longitudinal displacement and maintaining said pull rodmeans in frictional engagement with said O-ring means; gimbal meansspacedly mounted from said pull rod means carrying said roller means;frame support means coaxially and slidably securing said gimbal means;and a lever arm attached to said gimbal means adapted to rotate saidgimbal means with respect to said frame means.

5. A pull and rotation mechanism for a crystal growing apparatuscomprising, in combination: driving means; shaft means rotatably drivenby said driving means; annular frictional coupling means formed ofelastic mate rial surrounding portions of said shaft means; pull rodmeans; means securing said pull rod means for rotation and longitudinaldisplacement; elastic roller means rotatably mounted and in drivingengagement with said pull rod means; said pull rod means having alongitudinal axis displosed parallel to the same axis of said shaftmeans and being frictionally suspended between said frictional couplingmeans and said roller means; means securing said roller means forangular variation of the longitudinal axis of said roller in respect tosaid axis of said pull rod means so that upon changing the angularrelation of said axes a force component is exerted on the pull rod meansto longitudinally displace said pull rod means.

References Cited in the file of this patent UNITED STATES PATENTS722,977 Hall Mar. 17, 1903 2,281,277 Fitz Gerald Apr. 28, 1942 2,894,401Stal July 14, 1959 2,940,322 Uhing June 14, 1960 FOREIGN PATENTS 710,135Great Britain June 9, 1954

1. A PULL AND ROTATION MECHANISM FOR CRYSTAL GROWING APPARATUSCOMPRISING, IN COMBINATION; DRIVING MEANS; SHAFT MEANS ROTATABLY DRIVENBY SAID DRIVING MEANS; ANNULAR FRICTIONAL COUPLING MEANS FORMED OFELASTIC MATERIAL SURROUNDING PORTIONS OF SAID SHAFT MEANS; PULL RODMEANS MOUNTED FOR ROTATION AND LONGITUDINAL DISPLACEMENT; MOUNTING MEANSMAINTAINING SAID PULL ROD MEANS IN FRICTIONAL ENGAGEMENT WITH SAIDFRICTIONAL COUPLING MEANS; ROLLER MEANS ROTATABLY MOUNTED AND IN DRIVINGENGAGEMENT WITH SAID PULL ROD MEANS; GIMBAL MEANS ROTATABLY CONSTRUCTEDAND ARRANGED TO CARRY SAID ROLLER MEANS FOR ANGULAR VARIATION OF THELONGITUDINAL AXIS OF THE ROLLER IN RESPECT TO SAID AXIS OF THE PULL RODMEANS SO THAT UPON CHANGING THE ANGULAR RELATION OF THE AXES A FORCECOM-